Ghost cancellation reference signal with bessel chirps &amp; PN sequences, &amp; TV receiver using such signal

ABSTRACT

Composite ghost cancellation reference (GCR) signals that make available both a chirp and a PN sequence during the same vertical-blanking-interval (VBI) scan line in each successive field facilitate more rapid and efficient calculations of ghost cancellation and of equalization, on a continuing basis. A television receiver for use with such composite GCR signals includes circuitry for separating the chirp and PN sequence portions of the GCR signals from the remainder of the composite video signal, a ghost cancellation filter and an equalization filter connected in cascade to respond to the composite video signal and provided each with adjustable filtering weights, and a computer. Random-access memory addressed during writing snatches the vertical-blanking-interval scan lines selected to include GCR signals. Sets of four successive ones of the selected scan lines are then additively and subtractively combined to separate the chirp portions of the GCR signals from a remainder of the composite video signal. 
     The sets of selected scan lines are additively and subtractively combined in another way to separate the PN sequence portions of the GCR signals form a remainder of the composite video signal. The computer responds to the separated chirp portions of the GCR signals to calculate a discrete Fourier transform (DFT) therefrom. The computer proceeds from that DFT to determine the adjustable filtering weights of the ghost cancellation filter. The computer thereafter responds to the separated PN sequences to determine the adjustable filtering weights of the equalization filter.

This is a divisional of co-pending application Ser. No. 08/158,299,filed Nov. 29, 1993, which is a continuation-in-part of U.S. patentapplication Ser. No. 07/872,077, filed Apr. 22, 1992, abandoned, andU.S. patent application Ser. No. 07/984,488, filed Dec. 2, 1992,abandoned.

The invention relates to ghost cancellation reference (GCR) signals foruse in a television receiver and to a television receiver employingthose GCR signals.

BACKGROUND OF THE INVENTION

At the time U.S. patent application Ser. No. 07/872,077 was filedSubcommittee T-3 of the Advanced Television Systems Committee wasmeeting to determine a GCR signal for use in the United States. The GCRsignal was to be a compromise based from two GCR signals, one usingBessel pulse chirp signals as proposed by U.S. Philips Corp. and oneusing pseudo noise (PN) sequences as proposed by the David SarnoffResearch Center (DSRC) of Stanford Research Institute. The GCR signalsare inserted into selected vertical blanking intervals (VBIs). The GCRsignals are used in a television receiver for calculating the adjustableweighting coefficients of a ghost-cancellation filter through which thecomposite video signals from the video detector are passed to supply aresponse in which ghosts are suppressed. The weighting coefficients ofthis ghost-cancellation filter are adjusted so it has a filtercharacteristic complementary to that of the transmission medium givingrise to the ghosts. The GCR signals can be further used for calculatingthe adjustable weighting coefficients of an equalization filterconnected in cascade with the ghost-cancellation filter, for providingan essentially flat frequency spectrum response over the completetransmission path through the transmitter vestigial-sidebandamplitude-modulator, the transmission medium, the television receiverfront-end and the cascaded ghost-cancellation and equalization filters.

In the conventional method for cancelling ghosts in a televisionreceiver, the discrete Fourier transform (DFT) of the ghosted GCR signalis divided by the DFT of the non-ghosted GCR signal (which latter DFT isknown at the receiver from prior agreement with the transmitter) toobtain as a quotient the DFT transform of the transmission medium givingrise to ghosting; and the inverse DFT of this quotient is then used todefine the filter weighting coefficients of a compensatingghost-cancellation filter through which the ghosted composite videosignal is passed to obtain a de-ghosted composite video signal. Toimplement the DFT procedure efficiently, in terms of hardware or ofcalculations required in software, an integral power of twoequal-bandwidth frequency bins are used in the DFT. The distribution ofenergy in the Philips chirp signal has a frequency spectrum extendingcontinuously across the composite video signal band, in contrast to theDSRC PN sequence in which the distribution of energy does not extendcontinuously across the composite video signal band, but exhibits nullsin its frequency distribution. Accordingly, when the number ofequal-bandwidth frequency bins in the DFT is reduced in order to speedcalculation time, more accurate ghost cancellation is obtained with thechirp than with the PN sequence as GCR signal, the inventors observe.

During official testing by the Subcommittee, the DSRC GCR signal hasexhibited somewhat better performance in regard to equalization of thepassband after ghosting, which some experts including the Philipsengineers, attribute to better filter hardware. Theoretically,equalization calculated over an entire active portion of the VBI,proceeding from the PN sequence, has an accuracy substantially the sameas the accuracy available calculating equalization from the chirpsignal. The entire length of the Philips chirp signal is needed to havethe requisite information to implement equalization over the fullcomposite video signal band. The PN sequence contains pulse transitionseach of which transitions has substantially the entire frequencyspectrum contained therein. The PN sequence contains many pulsetransitions, each of which transitions has component frequenciesextending over substantially the entire frequency spectrum. Thisproperty of the PN sequence, the inventors observe, permits thecalculation of equalization taking samples at a prescribed samplingdensity only over a limited extent of the GCR signal. Taking samplesover only a portion of the GCR signal causes some loss in the accuracywith which equalization can be calculated, particularly under poorsignal-to-noise conditions. However, since the number of samplesinvolved in the calculation of weighting coefficients for theequalization filter is reduced, there can be an appreciable increase inthe speed with which equalization can be calculated, presuming thecalculation is done using an iterative method such as least-mean-squareserror reduction. Also, there is reduced complexity, in terms of hardwareor of calculations required in software, with regard to calculating theequalization filter weighting coefficients.

At the time U.S. patent application Ser. No. 07/872,077 was filed thecomposite GCR signals comprised of chirps and PN sequence signals thathad been proposed did not make available both a chirp and a PN sequenceduring the same VBI scan line. Subsequently, the Republic of China hasadopted a standard GCR signal in which both a chirp and a PN sequenceoccur during a VBI scan line in each successive field.

SUMMARY OF THE INVENTION

The inventors observe that making both a chirp and a PN sequenceavailable during each of selected VBI scan lines (e.g., a prescribed VBIscan line in each successive field, facilitates the more rapid andefficient calculations of ghost cancellation and of equalization, on acontinuing basis, particularly when the transmission medium exhibitscontinual change—e.g., during the rapidly changing ghost conditionscaused in over-the-air transmissions by overflying aircraft.

A television receiver embodying the invention in one of its aspectsincludes means for separating the chirp and PN sequence portions of theghost cancellation reference (GCR) signal from the remainder of thecomposite video signal, a ghost cancellation filter and an equalizationfilter connected in cascade to respond to the composite video signal andprovided each with adjustable filtering weights, means responding to theseparated chirp portion of the GCR signal to calculate its discreteFourier transform (DFT), means responding to that DFT to determine theadjustable filtering weights of the ghost cancellation filter, and meansresponding to the separated PN sequence to determine the adjustablefiltering weights of the equalization filter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D are waveforms of the ghost cancellationreference signals in selected vertical blanking intervals of foursuccessive fields of video, as embody the invention in one of itsaspects.

FIG. 2 is the waveform of a separated chirp signal as formed bydifferentially combining the sum of the ghost cancellation referencesignals of FIGS. 1A and 1B with the sum of the ghost cancellationreference signals of FIGS. 1C and 1D.

FIG. 3 is the waveform of a separated PN sequence as formed bydifferentially combining the sum of the ghost cancellation referencesignals of FIGS. 1A and 1D with the sum of the ghost cancellationreference signals of FIGS. 1B and 1C.

FIG. 4 is a schematic diagram of a television modulator arranged fortransmitting the signals of FIGS. 1A, 1B, 1C and 1D.

FIG. 5 is a schematic diagram of a television receiver arranged toreceive television signals incorporating the ghost cancellationreference signals of FIGS. 1A, 1B, 1C and 1D, to a suppress ghostsaccompanying those television signals and to equalize the transmissionchannel across the video bandwidth.

FIG. 6 is a schematic diagram of the GCR signal capture processor shownas a block in FIG. 5.

FIGS. 7A, 7B, 7C and 7D are waveforms of the ghost cancellationreference signals in selected vertical blanking intervals of foursuccessive fields of video, as embody the invention in one of itsaspects, alternative to the aspect of the invention illustrated by FIGS.1A, 1B, 1C and 1D.

FIG. 8 is the waveform of a separated chirp signal as formed bycombining the ghost cancellation reference signals of FIGS. 7B and 7C,of FIGS. 7D and 7A, or FIGS. 7A, 7B, 7C and 7D.

FIG. 9 is the waveform of a separated PN sequence preceded by a “gray”pedestal, as formed by combining the ghost cancellation referencesignals of FIGS. 7A, 7B, 7C and 7D.

FIG. 10 is a schematic diagram of the FIG. 6 serial processor forprocessing the ghost cancellation reference signals of FIGS. 1A, 1B, 1Cand 1D to generate FIG. 2 and FIG. 3 signals.

FIG. 11 is a schematic diagram of the FIG. 6 serial processor forprocessing the ghost cancellation reference signals of FIGS. 7A, 7B, 7Cand 7D to generate the FIG. 8 and FIG. 9 signals.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIGS. 1A, 1B, 1C and 1D show the ghost cancellation reference signals inselected scan lines of the vertical blanking intervals of foursuccessive fields of video. Insertion may be into any one (or more) ofthe 11th through 20th scan lines of each field, the present preferencebeing to replace the vertical interval reference (VIR) signal currentlyused in the 19th scan line of each field. To simplify the descriptionthat follows, insertion of GCR signal into the 19th scan line of eachfield will be assumed by way of specific illustration.

The ghost cancellation reference signals of FIGS. 1A, 1B, 1C and 1Dbegin with horizontal synchronization pulses 11, 21, 31 and 41,respectively, which pulses are shown as being negative-going. Theleading edges of the horizontal synchronization pulses are considered tobe the beginning of VBI scan lines that are each of 63.55 microsecondduration in NTSC standard television signals. The horizontalsynchronization pulses 11, 21, 31 and 41 are respectively followedduring ensuing back-porch intervals by chroma bursts 12, 22, 32 and 42.The plus and minus signs near the chroma bursts 12, 22, 32 and 42indicate their relative polarities respective to each other, per theNTSC standard.

Bessel pulse chirps 13, 23, 33 and 43 each of 33 microsecond durationbegin 12 microseconds into the VBI scan lines of FIGS. 1A, 1B, 1C and1D, respectively. The arrows associated with each of these chirps isindicative of its relative polarity with respect to the other chirps;chirp polarity is shown as alternating from frame to frame. These chirpsswing plus/minus 40 IRE from 30 IRE “gray” pedestals which extend from12 to 48 microseconds into these VBI lines. The gray level of thepedestals, the plus/minus swing of the chirps, the duration of thepedestals and the duration of the chirps have been specified tocorrespond as closely as possible to the Philips system that has beenofficially tested; and design variations were, at the time U.S. patentapplication Ser. No. 07/872,077 was filed, expected to occur should thecompromise GCR signals described herein be adopted by the Subcommitteeas their official recommendation for a standard.

Beginning at 51 microseconds into the VBI scan lines of FIGS. 1A, 1B, 1Cand 1D 127-sample PN sequences 14, 24, 34 and 44 respectively occur.Each of the PN sequences 14, 24, 34 and 44 is of the same 9-microsecondduration as the others. The PN sequence in the final field of each frameis of opposite polarity from the PN sequence in the initial field ofthat frame and is of the same polarity as the PN sequence in the initialfield of the next frame, as indicated by the arrows associated withrespective ones of the PN sequences 14, 24, 34 and 44. These PNsequences have −1 and +1 values at −15 IRE and +95 IRE levelsrespectively. These PN sequences have been specified to correspond asclosely as possible to the DSRC system that has been officially tested;and design variations were, at the time U.S. patent application Ser. No.07/872,077 was filed, expected to occur should the compromise GCRsignals described herein be adopted by the Subcommittee as theirofficial recommendation for a standard.

There was, at the time U.S. patent application Ser. No. 07/872,077 wasfiled, opinion within the Subcommittee that the Bessel pulse chirpshould be shortened to 17 microsecond duration so ghosts of up to 40microsecond delay can be cancelled without the restriction that the VBIline following that containing the GCR signal having not to haveinformation therein that changes from field to field. If the Besselpulse chirp is shortened, the PN sequence could be made to be 255 pulsesample times, rather than 127 pulse sample times, in length. Adjustmentsto the compromise GCR signals described herein may be made so the swingsof the Bessel pulse chirp and the PN sequence correspond, with suitableadjustment of the gray pedestal, if appropriate. The inventors favor thechirp swing being increased to extend over the range between the −15 IREand +95 IRE levels and the gray pedestal being set at 40 IRE. The lesserrange for the chirps was chosen by the Philips engineers for fear ofoverswing under some conditions, but the inventors believe that IFamplifier AGC will forestall such overswing. Extending the gray pedestalto the beginning of the PN sequence will then provide a signal that whenlow-pass filtered and subsequently gated during the mid-portion of thescan line Will provide a level that is descriptive of 40 IRE level andcan be used for automatic gain control of the composite video signal.

FIG. 2 shows the separated Bessel pulse chirp waveform that results whenthe GCR signals from two successive fields that are in two successiveframes are differentially combined, assuming that the GCR signals are ofthe sort shown in FIGS. 1A, 1B, 1C and 1D. A separated Bessel pulsechirp waveform per FIG. 2 results when the GCR signals of FIGS. 1B and1C are differentially combined. A separated Bessel pulse chirp waveformper FIG. 2 also results when the GCR signals of FIGS. 1D and 1A aredifferentially combined. A separated Bessel pulse chirp waveform perFIG. 2 also results when the sum of the GCR signals of FIGS. 1A and 1Bis differentially combined with the sum of GCR signals of FIGS. 1C and1D.

FIG. 3 shows the waveform that results when the sum of the GCR signalsof FIGS. 1A and 1D is differentially combined with he sum of GCR signalsof FIGS. 1B and 1C. The Bessel pulse chirp waveform, the “gray” pedestaland the chroma burst are suppressed in this signal; and DC informationconcerning 0 IRE level is lost. The PN sequence is maintained as aseparated PN sequence signal.

FIG. 4 shows in block schematic form a television transmitter for NTSCcolor television signals into which are inserted GCR signals per FIGS.1A, 1B, 1C and 1D.

A processing amplifier 50 generates composite video signals proceedingfrom color video signals and synchronizing signals. By way of example,the color video signals may be red (R), green (G) and blue (B) signalsfrom a studio color camera and the synchronizing signals may be from astudio sync generator that also supplies synchronizing signals to thestudio color camera. Alternatively, the color video signals may be froma remote location and the synchronizing signals furnished by a genlockconnection. Or, if the local transmitter is a low-power transmitterre-broadcasting signals received over-the-air from a distant high-powertransmitter, the color video signals may be generated by demodulatingthe received composite video signal and the synchronizing signals may beseparated from the received composite video signal.

The processing amplifier 50 is shown as including a crystal oscillator51 furnishing oscillations at eight times color carrier frequency f_(c),a counter 52 for counting the number of these oscillations perhorizontal scan line, a counter 53 for counting scan lines per field,and a counter 54 for counting modulo-four successive fields of videosignal. The processing amplifier 50 supplies its composite video outputsignal as a first input signal to an analog selector switch 55. Theoutput signal from the analog selector switch 55 is supplied to a videomodulator 56 to control the vestigial-sideband amplitude modulation ofthe video carrier. Sound signal is supplied to a frequency modulator 57.The modulated video and sound carriers are amplified by radio-frequencyamplifiers 58 and 59, respectively, and the output signals from theamplifiers 58 and 59 are combined in a coupling network 60 to abroadcast antenna 60. A number of cariants of the conventionaltelevision transmitter arrangements described in this and the previousparagraph are known to those familiar with television transmitterdesign.

The analog selector switch 55 corresponds to that previously known forinserting the vertical interval reference (VIR) signal. A decoder 62detects those portions of the count from the counter 52 associated withthe “active” portions of horizontal scan lines i.e., the portions ofhorizontal scan lines exclusive of the horizontal blanking intervals -to generate a logic ONE. A decoder 63 responds to the scan line countfrom the counter 53 to decode the occurrence of the 19th scan line ineach field and generate a logic ONE. An AND gate 64 responds to theselogic ONEs occurring simultaneously to condition the analog selectorswitch 55 to select a second input signal for application to the videomodulator 56, rather than the composite video signal furnished from theprocessing amplifier 50 to the analog selector switch 55 as its firstinput signal. This second signal is not the VIR signal, however, but isin successive fields successive ones of the GCR signals depicted inFIGS. 1A, 1B, 1C and 1D (or, alternatively, in FIGS. 7A, 7B, 7C and 7D).

These GCR signals are stored in digitized form in a read-only memory 65.A first portion of the address for the ROM 65 is supplied from thecounter 54, the modulo-four field count selecting which of the GCRsignals depicted in FIGS. 1A, 1B, 1C and 1D is to be inserted in thecurrent field. A second portion of the address for the ROM 65 issupplied from the counter 52 and scans the selected one of the GCRsignals depicted in FIGS. 1A, 1B, 1C and 1D. The digitized GCR signalread from the ROM 65 is supplied to a digital-to-analog converter 66.The resulting analog GCR signal is supplied as the second input signalto the analog selector switch 55 for insertion into the “active” portionof the 19th line of the field.

FIG. 5 depicts a television receiver arranged to receive televisionsignals incorporating the ghost cancellation reference signals of FIGS.1A, 1B, 1C and 1D. Television signals collected by an antenna 70 areamplified by a radio-frequency amplifier 71 and then down-converted toan intermediate frequency by a converter 72. An intermediate-frequencyamplifier 73 supplies to a video detector 74 and to a sound detector 75amplified response to the intermediate-frequency signals from theconverter 72. The sound detector 75 demodulates the frequency-modulatedsound carrier and supplies the resulting sound detection result to audioelectronics 76. The audio electronics 76, which may include stereophonicsound detection circuitry, includes amplifiers for supplying amplifiedsound-descriptive electric signals to loudspeakers 77 and 78.

The video detector 74 supplies analog composite video signal to ananalog-to-digital converter 79, to a burst detector 80, to a horizontalsync separator 81 and to a vertical sync separator 82. The separatedhorizontal synchronizing pulses from the horizontal sync separator 81and the separated vertical synchronizing pulses from the vertical syncseparator 82 are supplied to kinescope deflection circuitry 83, whichgenerates deflection signals for a kinescope 84. A burst gate generator85 generates a burst gate signal an appropriate interval after eachhorizontal sync pulse it is supplied from the horizontal sync separator81. This burst gate signal keys the burst detector 80 into operationduring chroma burst interval. The burst detector 80 is included in aphasi-locking loop for a phase-locked oscillator 86. The phase-lockedoscillator 86 oscillates at a frequency sufficiently high that theanalog-to-digital converter 79 sampling the analog composite videosignal from the video detector 74 once with each oscillationover-samples that signal. As is well-known, it is convenient from thestandpoint of simpler digital hardware design that phase-lockedoscillator 86 oscillate at a frequency that is an integral power of twogreater than the 3.58 MHz color subcarrier frequency. Sampling chromasignals four or eight times per cycle is preferred.

The separated horizontal sync pulses from the horizontal sync separator81 are supplied to a scan line counter 87 for counting, the scan linecount from which counter 87 is reset to zero at the outset of eachvertical sync interval by separated vertical sync pulses from thevertical sync separator 82. Indication in the count from the counter 87of the occurence of the 19th scan line in each field is detected by adecoder 88. Indication in the count from the counter 87 of the occurenceof the 20th scan line in each field is detected by a decoder 89. Theoccurences of the 19th and 20th scan line in each field is signaled to aGCR signal capture processor 90, which captures the GCR signals in the19th scan line of each field of digital composite video signal from theanalog-to-digital converter 79. This capturing process will be describedin greater detail in connection with the description of FIG. 6.

The GCR signal capture processor 90 includes circuitry for separatingthe Bessel pulse chirp portion of the captured GCR signals, whichportion is supplied to a ghost-cancellation filter weight computer 91.The GCR signal capture processor 90 also includes circuitry forseparating the PN sequence portion of the captured GCR signals, whichportion is supplied to an equalization filter weight computer 92. Thedigitized composite video signal from the analog-to-digital converter 79is supplied via a cascade connection of a ghost-cancellation filter 93and an equalization filter 94 to a luma/chroma separator 95. Theghost-cancellation filter 93 has filtering weights adjustable inresponse to results of the computations by the ghost-cancellation filterweight computer 91, and the equalization filter 94 has filtering weightsadjustable in response to results of the computations by theequalization filter weight computer 92.

The ghost-cancellation filter weight computer 91 is preferably of a typein which the discrete fourier transform Transform (DFT) of the ghostedGCR signal is divided by the DFT of the non-ghosted GCR signal to obtainas a quotient the DFT transform of the transmission medium giving riseto ghosting; and the inverse DFT of this quotient is then used to definethe filter weighing coefficients of a compensating ghost-cancellationfilter. As known by those skilled in the ghost-cancellation art, theghost-cancellation filter 93 is preferably of a type with a sparsekernel where the positioning of the non-zero filter weights can beshifted responsive to results from the ghost-cancellation filter weightcomputer 91. A ghost-cancellation filter with a dense kernel wouldtypically require 2048 filter weights, which would be difficult toconstruct in actual practice.

The equalization filter weight computer 92 could be of a type performingcalculations using DFTs, the results of which are subject to inverse-DFTin order to define the filter weighing coefficients of a compensatingequalization filter 94. Preferably, however, the equalization filterweight computer 92 is of a type using a least-mean-square error methodto perform an interative adjustment of a 15-tap or so digital FIR filterused as the equalization filter 94, adjustment being made so that thereis a best match to the (sin x)/x function of the result of correlatingof a portion of the de-ghosted PN sequence with the correspondingportion of the PN sequence known at the receiver as being a standard.

The luma/chroma separator 95 is preferably of a type using digital combfiltering for separating a digital luminance signal and a digital chromasignal from each other, which signals are respectively supplied todigital luminance processing circuitry 96 and to digital chrominanceprocessing circuitry 97. The digital luminance (Y) signal from thedigital luminance processing circuitry 96 and the digital I and Qsignals from the digital chrominance processing circuitry 97 aresupplied to a digital color matrixing circuit 98. Matrixing circuit 98responds to the digital Y, I and Q signals to supply digital red (R),green (G) and blue (B) signals to digital-to-analog converters 99, 100and 101, respectively. Analog red (R), green (G) and blue (B) signalsare supplied from the digital-to-analog converters 99, 100 and 101 to R,G and B kinescope driver amplifiers 102, 103 and 104, respectively. TheR, G and B kinescope driver amplifiers 102, 103 and 104 supply red (R),green (G) and blue (B) drive signals to the kinescope 84.

The filter 94 has thusfar been termed an “equalization filter” andconsidered to be a filter that would provide a flat frequency responsethrough the band, which is the way this filter has been characterized byother workers in the ghost-cancellation art. In practice it ispreferable to adjust the filter weights in the filter 94, not for flatfrequency response through the band, but with a frequency response knownto provide some transient over- and under-shooting, or video peaking.This reduces the need for providing transient overshooting or videopeaking in the digital luma processing circuitry 96.

FIG. 6 shows a representative way of constructing the GCR signal captureprocessor 90. Random access memories 111, 112, 113 and 114 are arrangedto serve as line stores for the GCR reference signals supplied duringfields 00, 01, 10 and 11 of each cycle of four successive fields ofdigitized composite video signal. These GCR reference signals aresupplied to the respective input ports of the RAMs 111, 112, 113 and 114from the analog-to-digital converter 79. The four successive fields ineach cycle are counted modulo-4 by a two-stage binary counter 115 thatcounts the ONEs generated by a decoder 116 that detects indications ofthe last scan line in a field furnished by the scan line count from thecounter 87. As a preparatory measure in the procedure of updating thefilter weighting coefficients in the ghost-cancellation filter 93 and inthe equalization filter 94, the proper phasing of the modulo-4 fieldcount can usually be determined by correlating the most recentlyreceived GCR signal, as de-ghosted, with each of the four standard GCRsignals stored in the receiver, looking for best match. Decoders 121,122, 123 and 124 decode the 100, 101, 110 and 111 signals as generatedby the 19th line decoder 88 supplying most significant bit and fieldcount from the field counter 115 supplying the two less significantbits, thereby to furnish write enable signals sequentially to the RAMs111, 112, 113 and 114 during the 19th scan lines of successive fields.

The RAMs 111, 112, 113 and 114 are addressed in parallel by an addresscounter 125 that counts the number of samples per scan line. The addresscounter 125 receives the oscillations from the phase-locked oscillator86 at its count input connection, and is reset by an edge of thehorizontal sync pulse. This addressing scan during the 19th scan lineallocates each successive digital composite video signal sample to asuccessive addressable location in the one of the RAMs 111, 112, 113 and114 receiving a write enable signal. During the 20th scan line thedecoder 89 provides a read enable signal to all of the RAMs 111, 112,113 and 114. The addressing scan the counter 125 provides the RAMs 111,112, 113 and 114 during the 20th scan line reads out the four mostrecently received and stored GCR signals parallely to a serial processor126 that combines them to generate sequential samples of a separatedBessel pulse chirp signal and sequential samples of a separated PNsequence.

During the 20th scan line, the decoder 89 also provides a write enablesignal to RAMs 127 and 128 that respectively serve as line stores forthe separated chirp signal and separated PN sequence. The decoder 89 atthe same time conditions address multiplexers 129 and 130 to selectaddresses from the address counter 125 as write addressing for the RAMs127 and 128 respectively. The counter 125 provides the RAM 127 theaddressing scan needed to write thereinto the sequential samples of theseparated chirp signal from the serial processor 126. The counter 125also provides the RAM 128 the addressing scan needed to write thereintothe sequential samples of the separated PN sequence from the serialprocessor 126. At times other than the 20th scan line, the addressmultiplexer 129 selects to the RAM 127 read addressing supplied to itsRA terminal from the ghost-cancellation filter weight computer 91 duringdata fetching operations, in which operations the computer 91 alsosupplies the RAM 127 a read enable signal. The RAM 127 supplies at timesother than the 20th scan line, the address multiplexer 130 selects tothe RAM 128 read addressing supplied to its RA terminal from theequalization filter weight computer 92 during data fetching operations,in which operations the computer 42 also supplies the RAM 128 a readenable signal. The RAMs 127 and 128 have respective O terminal forsupplying read output signals the ghost-cancellation filter weightcomputer 91 and to the equalization filter weight computer 92,respectively.

FIGS. 7A, 7B, 7C and 7D are waveforms of the ghost cancellationreference signals in selected vertical blanking intervals of foursuccessive fields of video, as embody the invention in one of itsaspects, alternative to the aspect of the invention which FIGS. 11A,11B, 11C and 11D concern. The GCR signals in FIGS. 7A and 7D are thesame as those of FIGS. 1A and 1D. The GCR signals in FIGS. 7B and 7Cdiffer from those of FIGS. 1B and 1C in that the swings of the PNsequences are reversed in direction. In FIGS. 7B and 7C the swings ofthe PN sequences 24′ and 34′ are in the same direction as the swings ofthe PN sequences 14 and 44 in FIGS. 7A and 7D.

FIG. 8 shows the separated Bessel pulse chirp waveform that results whenthe GCR signals from two successive fields that are in two successiveframes are differentially combined, assuming that the GCR signals are ofthe sort shown in FIGS. 7A, 7B, 7C and 7D. A separated Bessel pulsechirp waveform per FIG. 8 results when the GCR signals of FIGS. 7B and7C are differentially combined. A separated Bessel pulse chirp waveformper FIG. 8 also results when the GCR signals of FIGS. 7D and 7A aredifferentially combined. A separated Bessel pulse chirp waveform perFIG. 8 also results when the sum of the GCR signals of FIGS. 7A and 7Bis differentially combined with the sum of the GCR signals of FIGS. 7Cand 7D.

FIG. 9 shows the waveform that results when the GCR signals from four(or any multiple of four) successive fields are additively combined orare averaged, assuming that the GCR signals are of the sort shown inFIGS. 7A, 7B, 7C and 7D. The Bessel pulse chirp waveform and the chromaburst are suppressed in this signal. The DC level and “gray” pedestalare maintained in this signal as well as the PN sequence. The PNsequence can then be separated by high-pass digital filtering. The DClevel and “gray” pedestal can be separated by low-pass digitalfiltering. The DC level and “gray” pedestal are useful in circuitry forcontrolling the gain and DC-offset of the analog composite signalapplied to the analog-to-digital converter 79. Circuits are known in theprior art in which the digital output signal of an analog-to-digitalconverter is selected as input signal to a first digital comparatorduring a portion of the digitized composite video signal known to besupposedly at 0 IRE level, there to be compared against digitized ideal0 IRE level to develop a first digital error signal that is converted toanalog error by a digital-to-analog converter and fed back to degenerateerror in the 0 IRE level against which the input signal to theanalog-to-digital converter is DC-restored. In certain of these circuitsthe digital output signal of the same analog-to-digital converter isselected as input signal to a second digital comparator during a portionof the digitized composite video signal known to be supposedly at aprescribed pedestal level, there to be compared against the prescribedpedestal level in digital form to develop a second digital error signalthat is converted to analog error by a digital-to-analog converter andfed back as an automatic gain control (AGC) signal to a gain-controlledamplifier preceding the analog-to-digital converter and keeping theinput signal to the analog-to-digital converter quite exactly within thebounds of the conversion range.

FIG. 10 shows how the FIG. 6 serial processor may be constructed forprocessing the ghost cancellation reference signals of FIGS. 1A, 1B, 1CAND 1D to generate the FIG. 2 and FIG. 3 signals. A serial adder 131sums the RAM 111 output signal per FIG. 1A with the RAM 112 outputsignal per FIG. 1B. A serial adder 132 sums the RAM 113 output signalper FIG. 1C with the RAM 114 output signal per FIG. 1D. A serialsubtractor 133 subtracts the sum output of the adder 132 from the sumoutput of the adder 131 to generate a separated Bessel pulse chirpsignal. With a bit point shift of two places towards less significance,for carrying out wired division by four, this separated Bessel pulsechirp signal is the FIG. 2 signal. A serial adder 134 sums the RAM 111output signal per FIG. 1A with the RAM 114 output signal per FIG. 1D. Aserial adder 135 sums the RAM 112 output signal per FIG. 1B with the RAM113 output signal per FIG. 1C. A serial subtractor 136 subtracts the sumoutput of the adder 135 from the sum output of the adder 134 to generatea separated PN sequence signal. With a bit point shift of two placestowards less significance, for carrying out wired division by four, thisseparated PN sequence signal is the FIG. 3 signal.

FIG. 11 shows how the FIG. 6 serial processor may be constructed forprocessing the ghost cancellation reference signals of FIGS. 7A, 7B, 7Cand 7D to generate the FIG. 8 and FIG. 9 signals. Serial adders 131 and132 and serial subtractor 133 cooperate to generate a separated Besselpulse chirp signal, as described in connection with FIG. 10. With a bitpoint shift of two places towards less significance, for carrying outwired division by four, this separated Bessel pulse chirp signal is theFIG. 8 signal. A serial adder 137 sums the sum outputs of the adders 131and 132 to generate a separated PN sequence signal. With a bit pointshift of two places towards less significance, for carrying out wireddivision by four, this separated PN sequence signal is the FIG. 9signal.

The foregoing description assumes that only one VBI scan line per fieldis made available by television broadcasters. The availability of twosuccessive VBI scan lines in each field allows their being added tocancel color burst within the period of a single scan line, lesseningthe possibility that fast fading conditions will lead to imperfectcancellation of color burst or to misalignment of GCR signals when theyare combined. Also, the time required to acquire the data necessary forthe calculations of ghost cancellation and equalization parameters ishalved. By way of example, the GCR signals of FIGS. 1A and 1B could bein the 19th and the 20th scan lines of the first field of each frame;and the GCR signals of FIGS. 1C and 1D could be in the 19th and 20thscan lines of the second field of each frame. Alternatively, by way offurther example, the GCR signals of FIGS. 7A and 7B could be in the 19thand the 20th scan lines of the first field of each frame; and the GCRsignals of FIGS. 7C and 7D could be in the 19th and the 20th scan linesof the second field of each frame.

The FIG. 5 television receiver can be modified to include a 1H delayline connected at its input to receive video signal from the videodetector 74. This facilitates addition of the 19th and the 20th scanlines of each field being done in the analog regime by adding thesignals at the input and output of a 1H delay line to supply inputsignal to the ADC 79. Where the GCR signals of FIGS. 7A-7D are used, thecolor burst is cancelled and both the chirp and PN sequence signals arestrengthened prior to digitization by the ADC 79. This reduces errorsarising from round-off during digitization and from the sampling duringdigitization not being timed exactly the same from line to line. Thedecoders 88 and 89 are modified to detect scan lines 20 and 21, thustaking into account the delay introduced by the 1 H delay line.Alternatively, modifications of the FIG. 5 television receiver can besuch that the 19th and the 20th scan lines of each field are combined inthe digital regime; this is done through suitable modification of theGCR signal capture processor, changing the read and write addressing ofthe GCR line-store RAMs therein. Instead of including GCR signalcomponents in the 19th and the 20th scan lines of each field, GCR signalcan be included in the 18th and the 19th scan lines of each field. Instill other alternatives, GCR signal components are included in the 18thand the 20th scan lines of each field, so that horizontal sync as wellas color burst portions of the signal can be suppressed bydifferentially combining the corresponding pixels of the two scan lines,while anti-phase chirp or PN sequence components combine constructively.

The voluntary standard for GCR signals in the United States is now theU.S. Philips Corp. proposal using Bessel chirps. The voluntary standardis described in a paper by L. D. Claudy and S. Herman entitled “GHOSTCANCELING: A New Standard for NTSC Broadcast Television” and presented17 Sep. 1992 at the IEEE Broadcast Technology Symposium in WashingtonD.C. The foregoing teachings in regard to television receiver designhave application to GCR signals per the voluntary standard, particularlywith regard to the GCR signal capture processor and to the extraction ofchirp pedestal information. The GCR signals of the voluntary standardare inserted into the 19th line of each field and repeat in aneight-field cycle, rather than the four-field cycle explicitly describedabove. The GCR signal capture processor 90 as shown in FIG. 6 is readilymodified to augment the modulo-4 field counter 115 with an additionalcounter stage or two, thereby to provide a modulo-8 field counter or amodulo-16 field counter; to add additional GCR signal line store RAMsfor storing one or two eight-field cycles of the GCR signals of thevoluntary standard; and to add field-count decoders for selectivelywriting the additional GCR signal line store RAMs. Initial roughcalculations of ghost cancellation parameters may be made by combiningonly a pair of the GCR signals of the voluntary standard, so as toseparate chirp signal, with a greater number of pairs of GCR signalsbeing combined later on to support refined calculations of ghostcancellation parameters. The computation of equalizing parameters forapplication to the equalization filter 94 is done proceeding from theseparated Bessel chirp, rather than from a separated PN sequence, ofcourse.

Further refinements in the inventor's GCR signal capture processor aredescribed in their U.S. patent application Ser. No. 07/984,488 filed 2Dec. 1992 and entitled GHOST CANCELATION REFERENCE SIGNAL ACQUISITIONCIRCUITRY, AS FOR TV RECEIVER OR VIDEO RECORDER, the drawing andspecification of which are appended hereto for incorporation herein.

One skilled in the art of electronic circuits and systems design andacquainted with the foregoing disclosure will be enabled to design anumber of variants of the signals and circuits specifically disclosed;and this should be borne in mind when considering the respective scopesof the claims which follow.

Appendix

What is claimed is:
 1. A television receiver for use withghost-cancellation-reference signals of a type that include both a chirpand a pseudo-noise sequence in a selected scan line of a verticalblanking interval of each field of a composite video signal, saidtelevision receiver comprising: means for separating the chirp andpseudo-noise sequence portions of the ghost-cancellation-referencesignals from the remainder of the composite video signal; and a ghostcancellation filter provided with adjustable filtering weights; anequalization filter provided with adjustable filtering weights andconnected in cascade with said ghost cancellation filter to respond tothe composite video signal; means responding to the separated chirpportions of the ghost-cancellation-reference signals to calculate adiscrete Fourier transform therefrom; means responding to said discreteFourier transform to determine values of the adjustable filteringweights of the ghost cancellation filter; and means responding to theseparated pseudo-noise sequence portions of theghost-cancellation-reference signals to determine values of theadjustable filtering weights of the equalization filter.
 2. A televisionreceiver as set forth in claim 1, wherein said means for separating thechirp and pseudo noise sequence portions of theghost-cancellation-reference signals from the remainder of the compositevideo signal comprises: means for selecting scan lines with saidghost-cancellation-reference signals from the vertical blanking intervalof each field; means for additively and subtractively combining selectedscan lines in sets of four successive ones of said selected scan lines,so as to separate the chirp portions of the ghost-cancellation-referencesignals from a remainder of the composite video signal; and means foradditively and subtractively combining selected scan lines in sets offour successive ones of said selected scan lines, so as to separate thepseudo noise sequence portions of the ghost-cancellation-referencesignals from a remainder of the composite video signal.
 3. A televisionreceiver for receiving television signals of a type wherein a compositevideo signal including a ghost-cancellation reference signal therewithinis transmitted, said ghost-cancellation reference signal includingwithin an active portion of each of selected scan lines both a chirpsignal and a subsequent pseudo-noise sequence, wherein in each pair ofsuccessive pairs of said selected scan lines both scan lines haverespective chirp signals of the same sense as each other, wherein withineach said pair of selected scan lines the two scan lines have respectivepseudo noise sequences of opposite sense to each other, whereinsuccessive ones of said selected scan lines occur in successive verticalblanking intervals of said composite video signal, and wherein the twoselected scan lines in each succeeding said pair of selected scan lineshave respective chirp signals of opposite sense to the respective chirpsignals in the preceding said pair of selected scan lines, saidtelevision receiver comprising: means for responding to a selected oneof said television signals to supply said composite video signal; meansfor additively and subtractively combining selected scan lines in setsof four successive ones of said selected scan lines so as to separatechirp portions of the ghost-cancellation-reference signals from aremainder of said composite video signal; means for additively andsubtractively combining selected scan lines in sets of four successiveones of said selected scan lines so as to separate the pseudo noisesequence portions of the ghost-cancellation-reference signals from aremainder of said composite video signal; a ghost cancellation filterprovided with adjustable filtering weights; an equalization filterprovided with adjustable filtering weights and connected in cascade withsaid ghost cancellation filter to respond to said composite videosignal; means responding to the separated chirp portions of theghost-cancellation-reference signals to calculate a discrete Fouriertransform therefrom; means responding to said discrete Fourier transformto determine values of the adjustable filtering weights of the ghostcancellation filter; and means responding to the separated pseudo noisesequence portions to determine values of the adjustable filteringweights of the equalization filter.
 4. A television receiver fortelevision signals including ghost-cancellation-reference signals of atype that include chirp information comprising a single chirp withpedestal in a selected scan line of the vertical blanking interval ofeach field, consecutive ones of which chirps alternate being first andsecond senses in a prescribed pattern, said television receivercomprising: means for responding to a selected one of said televisionsignals to supply a composite video signal; means for separating thechirp information from a remainder of said composite video signal,including; means for selecting an even-numbered plurality of said scanlines with chirps from respective ones of said vertical blankingintervals, and means for combining corresponding samples of saideven-numbered plurality of said selected scan lines to generaterespective samples of said chirp information without accompanyingpedestal; a ghost cancellation filter provided with adjustable filteringweighs; and means responding to the separated chirp information forcomputing values for the adjustable filtering weights of the ghostcancellation filter.
 5. A television receiver as set forth in claim 4,wherein said means responding to the separated chirp information forcomputing values of the adjustable filtering weights of the ghostcancellation filter comprises: means responding to the separated chirpinformation of the ghost-cancellation-reference signals to calculate adiscrete Fourier transform therefrom; and means responding to saiddiscrete Fourier transform to determine the values of the adjustablefiltering weights of the ghost cancellation filter.
 6. A televisionreceiver as set forth in claim 5 wherein said even-numbered plurality ofsaid selected scan lines includes four scan lines.
 7. A televisionreceiver as set forth in claim 5 wherein said even-numbered plurality ofsaid selected scan lines includes a multiple of four scan lines.
 8. Atelevision receiver as set forth in claim 4 wherein said even-numberedplurality of said selected scan lines includes four scan lines.
 9. Atelevision receiver as set forth in claim 4 wherein said even-numberedplurality of said selected scan lines includes a multiple of four scanlines.
 10. A television receiver as set forth in claim 4, includingmeans for separating information concerning the pedestals of said chirpinformation, separated from said chirp information, which meanscomprises: means for selecting an even-numbered plurality of said scanlines with chirps from respective ones of said vertical blankingintervals, and means for combining corresponding samples of saideven-numbered plurality of said selected scan lines to generaterespective samples of said information concerning the pedestals of saidchirp information, separated from said chirp information.
 11. Atelevision receiver for television signals includingghost-cancellation-reference signals of a type that include chirpinformation and pedestal information together comprising a single chirpwith pedestal in a selected scan line of a vertical blanking interval ofeach field, consecutive ones of which chirps alternate being first andsecond senses in a prescribed pattern, said television receiverincluding: means for responding to a selected one of said televisionsignals to supply a composite video signal; means for separating saidpedestal information from said chirp information, which means comprises:means for selecting an even-numbered plurality of said scan lines withchirps from respective ones of said vertical blanking intervals, andmeans for combining corresponding samples of said even-numberedplurality of said selected scan lines to generate respective samples ofsaid pedestal information separated from said chirp information.
 12. Atelevision receiver for television signals includingghost-cancellation-reference signals of a type that include a singlechirp with pedestal in a selected scan line of the vertical blankinginterval of each field, consecutive ones of which chirps alternate beingfirst and second senses in a prescribed patter, said television receivercomprising: means for responding to a selected one of said televisionsignals to supply a composite video signal; means for separating chirpinformation from the remainder of the composite video signal, including:means for selecting an even-numbered plurality of said scan lines withchirps from respective ones of said vertical blanking intervals, saideven-numbered plurality being a multiple of four, each of which selectedscan lines includes front porch, horizontal synchronizing pulse, backporch, color burst and a pedestal for the chirp therewithin; means forcombining corresponding samples of said even-numbered plurality of saidselected scan lines to generate respective samples of said chirpinformation without accompanying front porch, horizontal synchronizingpulse, back porch, color burst or pedestal; a ghost cancellation filterprovided with adjustable filtering weights; and means responding to theseparated chirp information for computing values of the adjustablefiltering weights of the ghost cancellation filter.
 13. A communicationsystem, comprising: means for generating video signals; means forinserting ghost canceling reference signals in each vertical blankinginterval of said video signals, said ghost canceling reference signalscomprising pseudo-random noise sequences and chirp signals of differentpredefined signal characteristics; transmission means for enablingtransmission of said video signals containing said ghost cancelingreference signals; and ghost canceling means for enabling reception ofsaid video signals containing said ghost canceling reference signalstransmitted by said transmission means and processing said ghostcanceling reference signals contained in said received video signals toeliminate channel transmission delay distortion, said ghost cancelingmeans comprising: means for separating the chirp signals and thepseudo-random noise sequences of the ghost cancellation referencesignals from the received video signals; a ghost cancellation filterprovided with adjustable filtering weights; an equalization filterprovided with adjustable filtering weights and connected in cascade withsaid ghost cancellation filter to respond to the received video signals;means responding to the separated chirp signals to calculate a discreteFourier transform therefrom; means responding to said discrete Fouriertransform to determine the adjustable filtering weights of said ghostcancellation filter for enabling said ghost cancellation filter tocancel ghost components of said received video signals resulting fromsaid channel transmission delay distortion; and means responding to theseparated pseudo-random noise sequences to determine the adjustablefiltering weights of said equalization filter for enabling saidequalization filter to provide a flat spectrum over the entire frequencyrange for said ghost cancellation reference signals transmission.
 14. Acommunication system as claimed in claim 13, wherein said pseudo-randomnoise sequences and chirp signals are included within an active portionof each of selected scan lines in each vertical blanking interval, andwithin each of said selected scan lines in each vertical blankinginterval said chirp signals precede said pseudo-random noise sequences.15. An apparatus for receiving a plurality of signals divided into aplurality of cyclic fields, each including field synchronization signalsand a vertical blanking period which further includes a plurality ofhorizontal scanning periods, wherein at least two of said horizontalscanning periods in a single vertical blanking period include twodifferent reference signals, one of said reference signals being apseudo-random noise sequence and the other being a chirp signal, saidapparatus including a channel characterization means comprising: areference signal processing means for processing said received signalsincluding said two different reference signals in said two horizontalscanning periods within said single vertical blanking period, saidreference signal processing means comprising: means for separating saidchirp signal and said pseudo-random noise sequence of said referencesignals from said received signals; a ghost cancellation filter providedwith adjustable filtering weights; an equalization filter provided withadjustable filtering weights and connected in cascade with said ghostcancellation filter to respond to said received signals; meansresponding to the separated chirp signals of said reference signals tocalculate a discrete Fourier transform therefrom; means responding tosaid discrete Fourier transform to determine values of the adjustablefiltering weights of the ghost cancellation filter; and means respondingto the separated pseudo-random noise sequence of said reference signalsto determine values of the adjustable filtering weights of theequalization filter.
 16. The apparatus of claim 15, wherein said meansfor separating said chirp signal and said pseudo-random noise sequenceof said reference signals from said received signals comprises: meansfor selecting scan lines with said reference signals from said verticalblanking interval of each cyclic field; means for additively andsubtractively combining selected scan lines in sets of four successivehorizontal scanning periods so as to separate said chirp signal of saidreference signals from a remainder of said received signals; and meansfor additively and subtractively combining selected scan lines in setsof four successive horizontal scanning periods so as to separate saidpseudo-random noise sequence of said reference signals from a remainderof said received signals.
 17. A receiver for receiving a televisionsignal divided into a plurality of successive fields each comprising aprescribed number of lines of information, said lines being of uniformrespective duration, a prescribed single line of each of said fieldsincluding a first ghost-cancellation reference signal and a secondghost-cancellation reference signal different than said firstghost-cancellation reference signal, the relative phases of said firstand said second ghost-cancellation reference signals varying from fieldto field in prescribed pattern, said first ghost-cancellation referencesignal having a prescribed first duration longer than half a lineduration and said second ghost-cancellation reference signal comprisinga pseudo-noise (PN) sequence and having a prescribed second durationshorter than half a line duration, said receiver apparatus comprising:circuitry for separating said first ghost-cancellation reference signaland any ghosting thereof from said second ghost-cancellation referencesignal and any ghosting thereof; circuitry for characterizing areception channel responsive to said first ghost-cancellation referencesignal and said any ghosting thereof; and an adaptive filter for saidtelevision signal, the parameters of which adaptive filter are adjustedresponsive to said characterizing of the reception channel forsuppressing ghosting in the response of said adaptive filter.
 18. Thereceiver of claim 17, wherein said circuitry for characterizing thereception channel includes: a read-only memory operated to supply thediscrete Fourier transform of a first ideal signal corresponding to saidfirst ghost-cancellation reference signal without any attendantghosting; circuitry for calculating the discrete Fourier transform ofsaid first ghost-cancellation reference signal as received with ghostingand separated from said second ghost-cancellation reference signal, anddividing the terms of the discrete Fourier transform of said separatedfirst ghost-cancellation reference signal as received with ghosting bycorresponding terms of said discrete Fourier transform of said firstideal signal supplied from said read-only memory, thereby to generate adiscrete Fourier transform characterizing the reception channel.
 19. Thereceiver of claim 17, wherein said adaptive filter is a ghostcancellation filter, said receiver further comprising: circuitry forseparating said second ghost-cancellation reference signal and anyghosting thereof from said first ghost-cancellation reference signal andany ghosting thereof, a read-only memory operated to supply the discreteFourier transform of a second ideal signal corresponding to said secondghost-cancellation reference signal without any attendant ghosting;circuitry for calculating the discrete Fourier transform of said secondghost-cancellation reference signal as received with ghosting andseparated from said first ghost-cancellation reference signal, anddividing the terms of the discrete Fourier transform of said separatedsecond ghost-cancellation reference signal as received with ghosting bycorresponding terms of said discrete Fourier transform of a second idealsignal supplied from said read-only memory, thereby to generate adiscrete Fourier transform characterizing the reception channel; and afurther adaptive filter for said television signal, the parameters ofwhich adaptive filter are adjusted responsive to said characterizing ofthe reception channel, for reducing the departure of the spectralresponse of said reception channel from a desired spectral response. 20.The receiver of claim 17, wherein said adaptive filter is a ghostcancellation filter, said receiver further comprising: circuitry forseparating said second ghost-cancellation reference signal and anyghosting thereof from said first ghost-cancellation reference signal andany ghosting thereof; circuitry responsive to said secondghost-cancellation reference signal and said any ghosting thereof forcalculating the departure of the spectral response of said receptionchannel from a desired spectral response; and a further adaptive filterfor said television signal, the parameters of which adaptive filter areadjusted for reducing the departure of the spectral response of saidreception channel from said desired spectral response.
 21. A receivercomprising: detection circuitry for recovering a digitized basebandsignal by detecting a transmitted signal having a succession of frames,each of said frames comprising an odd-numbered field followed by aneven-numbered field, each of said fields comprising a specified numberof lines with only a particular one of said lines being designated tocarry a respective transmission equalization reference signal comprisinga first component transmission equalization reference signal and asecond component transmission equalization reference signal, said firstcomponent transmission equalization reference signals being of the sameamplitude and sense of polarity in both said odd-numbered field and saideven-numbered field of each said frame, said second componenttransmission equalization reference signals being the same in amplitudein both said odd-numbered field and said even-numbered field of eachsaid frame but opposite in sense of polarity; circuitry for separatingfrom said digitized baseband signal said lines designated for carrying arespective transmission equalization reference signal; memory fortemporarily storing a number of said designated lines as separated;combining circuitry for separating said second component transmissionequalization reference signal from said transmission equalizationreference signals by combining a most current one of said designatedlines with at least one temporarily stored previous one of saiddesignated lines; an equalization filter with adjustable filteringweights, said equalization filter connected for responding to saiddigitized baseband signal; and an equalization weight computerresponding to said second component transmission equalization referencesignal separated by said combining circuitry to determine saidadjustable filtering weights of the equalization filter.
 22. Thereceiver of claim 21, further characterized in that each said secondcomponent transmission equalization reference signal comprises apseudo-noise (PN) sequence of a prescribed first length.
 23. Thereceiver of claim 22, further characterized in that said combiningcircuitry is of a type for separating said PN sequences of saidprescribed first length from said transmission equalization referencesignals by differentially combining said designated lines that are indifferent fields of the same frame.
 24. The receiver of claim 21 furthercharacterized in that, in each said particular one of said lines that isdesignated for carrying a respective transmission equalization referencesignal, said second component transmission equalization reference signalis of shorter duration than said first component transmissionequalization reference signal.
 25. The receiver of claim 24 furthercharacterized in that, in each said particular one of said lines that isdesignated for carrying a respective transmission equalization referencesignal, said second component transmission equalization reference signalfollows said first component transmission equalization reference signal.26. The receiver of claim 25, further characterized in that each saidsecond component transmission equalization reference signal comprises apseudo-noise (PN) sequence of a prescribed first length.
 27. Thereceiver of claim 26, further characterized in that said combiningcircuitry is of a type for separating said PN sequences of saidprescribed first length from said transmission equalization referencesignals by differentially combining said designated lines that are indifferent fields of the same frame.
 28. The receiver of claim 24,further characterized in that each said second component transmissionequalization reference signal comprises a pseudo-noise (PN) sequence ofa prescribed first length.
 29. The receiver of claim 28, furthercharacterized in that said combining circuitry is of a type forseparating said PN sequences of said prescribed first length from saidtransmission equalization reference signals by differentially combiningsaid designated lines that are in different fields of the same frame.30. The receiver of claim 21, further characterized in that saidcombining circuitry is of a type for separating said second componenttransmission equalization reference signals by combining an even number,at least four, of said designated lines.
 31. The receiver of claim 30,further characterized in that each said second component transmissionequalization reference signal comprises a pseudo-noise (PN) sequence ofa prescribed first length.
 32. The receiver of claim 30 furthercharacterized in that, in each said particular one of said lines that isdesignated for carrying a respective transmission equalization referencesignal, said second component transmission equalization reference signalis of shorter duration than said first component transmissionequalization reference signal.
 33. The receiver of claim 32 furthercharacterized in that, in each said particular one of said lines that isdesignated for carrying a respective transmission equalization referencesignal, said second component transmission equalization reference signalfollows said first component transmission equalization reference signal.34. The receiver of claim 33, further characterized in that each saidsecond component transmission equalization reference signal comprises apseudo-noise (PN) sequence of a prescribed first length.
 35. A receivercomprising: circuitry for recovering a digitized baseband signal bydetecting a television signal having a succession of frames, each ofsaid frames comprising an odd-numbered field followed by aneven-numbered field, each of said fields comprising a specified numberof lines only a particular one of which said lines is designated forcarrying a respective ghost-cancellation reference signal comprising afirst component ghost-cancellation reference signal and a secondcomponent ghost-cancellation reference signal, said first componentghost-cancellation reference signals being of the same amplitude andsense of polarity in both said odd-numbered field and said even-numberedfield of each said frame, said second component ghost-cancellationreference signals being the same in amplitude in both said odd-numberedfield and said even-numbered field of each said frame but opposite insense of polarity; circuitry for separating from said digitized basebandsignal said lines designated for carrying a ghost-cancellation referencesignal; memory for temporarily storing a number of said designated linesas separated; combining circuitry for separating said second componentghost-cancellation reference signal from said designated lines bycombining a most current one of said designated lines with at least onetemporarily stored previous one of said designated lines; anequalization filter with adjustable filtering weights, said equalizationfilter connected for responding to said digitized baseband signal; andan equalization weight computer responding to said second componentghost-cancellation reference signal separated by said combiningcircuitry to determine said adjustable filtering weights of theequalization filter.
 36. The receiver of claim 35, further characterizedin that each said second component ghost-cancellation reference signalcomprises a pseudo-noise (PN) sequence of a prescribed first length. 37.The receiver of claim 36, further characterized in that said combiningcircuitry is of a type for separating said pseudo-noise (PN) sequencesof a prescribed first length from said ghost-cancellation referencesignals by differentially combining said designated lines that are inthe same frame.
 38. The receiver of claim 35 further characterized inthat, in each said particular one of said lines that is designated forcarrying a respective ghost-cancellation reference signal, said secondcomponent ghost-cancellation reference signal is of shorter durationthan said first component ghost-cancellation reference signal.
 39. Thereceiver of claim 35 further characterized in that, in each saidparticular one of said lines that is designated for carrying arespective ghost-cancellation reference signal, said second componentghost-cancellation reference signal follows said first componentghost-cancellation reference signal.
 40. The receiver of claim 31,further characterized in that each said second componentghost-cancellation reference signal comprises a pseudo-noise (PN)sequence of a prescribed first length.
 41. The receiver of claim 40,further characterized in that said combining circuitry is of a type forseparating said pseudo-noise (PN) sequences of said prescribed firstlength from said ghost-cancellation reference signals by differentiallycombining said designated lines that are in different fields of the sameframe.
 42. The receiver of claim 38, further characterized in that eachsaid second component ghost-cancellation reference signal comprises apseudo-noise (PN) sequence of a prescribed first length.
 43. Thereceiver of claim 42, further characterized in that said combiningcircuitry is of a type for separating said pseudo-noise (PN) sequencesof said prescribed first length from said ghost-cancellation referencesignals by differentially combining said designated lines that are indifferent fields of the same frame.
 44. The receiver of claim 35,further characterized in that said combining circuitry is of a type forseparating said second component ghost-cancellation reference signals bycombining an even number, at least four, of said designated lines. 45.The receiver of claim 44, further characterized in that each said secondcomponent ghost-cancellation reference signal comprises a pseudo-noise(PN) sequence of a prescribed first length.
 46. The receiver of claim 44further characterized in that, in each said particular one of said linesthat is designated for carrying a respective ghost-cancellationreference signal, said second component ghost-cancellation referencesignal is of shorter duration than said first componentghost-cancellation reference signal.
 47. The receiver of claim 46further characterized in that, in each said particular one of said linesthat is designated for carrying a respective ghost-cancellationreference signal, said second component ghost-cancellation referencesignal follows said first component ghost-cancellation reference signal.48. The receiver of claim 47, further characterized in that each saidsecond component ghost-cancellation reference signal comprises apseudo-noise (PN) sequence of a prescribed first length.
 49. A receivercomprising: detection circuitry for recovering a digitized basebandsignal by detecting a transmitted signal having a succession of frames,each of said frames comprising an odd-numbered field followed by aneven-numbered field, each of said fields comprising a specified numberof lines, a particular one of which said lines is designated forcarrying a respective transmission equalization reference signalcomprising a first component transmission equalization reference signaland a second component transmission equalization reference signal ofshorter duration than said first component transmission equalizationreference signal; separator circuitry for separating each of said firstand second component transmission equalization reference signals fromsaid digitized baseband signal; a ghost cancellation filter and anequalization filter connected in cascade for responding to saiddigitized baseband signal, each filter having adjustable filteringweights; and filter weight computation circuitry for determining saidadjustable filtering weights of said ghost cancellation filterresponsive to said first component transmission equalization referencesignals separated by said separator circuitry, and for determining saidadjustable filtering weights of said equalization filter responsive tosaid second component transmission equalization reference signalsseparated by said separator circuitry.
 50. The receiver of claim 49,further characterized in that said filter weight computation circuitrycomprises: a ghost cancellation filter weight computer responding tosaid first component transmission equalization reference signalsseparated by said separator circuitry to determine said adjustablefiltering weights of said ghost cancellation filter; and an equalizationfilter weight computer responding to said second component transmissionequalization reference signals separated by said separator circuitry todetermine said adjustable filtering weights of said equalization filter.51. The receiver of claim 50, further characterized in that said ghostcancellation filter weight computer is arranged to calculate a discreteFourier transform (DFT) in response to said first component transmissionequalization reference signals separated by said separator circuitry anddetermines said adjustable filtering weights of the ghost cancellationfilter from that DFT.
 52. The receiver of claim 49, furthercharacterized in that said separator circuitry is of a type forseparating said first component transmission equalization referencesignals by combining an even number at least four of said designatedlines.
 53. A receiver comprising: detection circuitry for recovering adigitized baseband signal by detecting a transmitted signal having asuccession of frames, each of said frames comprising an odd-numberedfield followed by an even-numbered field, each of said fields comprisinga specified number of lines, a particular one of which said lines isdesignated for carrying a respective transmission equalization referencesignal comprising a first component transmission equalization referencesignal and a second component transmission equalization reference signalof shorter duration than said first component transmission equalizationreference signal, said first component transmission equalizationreference signals being of the same amplitude and sense of polarity inboth said odd-numbered field and said even-numbered field of each saidframe, said second component transmission equalization reference signalsbeing the same in amplitude in both said odd-numbered field and saideven-numbered field of each said frame but opposite in sense ofpolarity; circuitry for separating from said digitized baseband signalsaid lines designated for carrying a transmission equalization referencesignal; memory for temporarily storing a number of said designated linesas separated; combining circuitry for separating from said transmissionequalization reference signals said first component transmissionequalization reference signal and said second component transmissionequalization reference signal by combining a most current one of saiddesignated lines with at least one temporarily stored previous one ofsaid designated lines; a ghost cancellation filter and an equalizationfilter connected in cascade for responding to said digitized basebandsignal, each filter having adjustable filtering weights; and filterweight computation circuitry for determining said adjustable filteringweights of said ghost cancellation filter responsive to said firstcomponent transmission equalization reference signals separated by saidcombining circuitry, and for determining said adjustable filteringweights of said equalization filter responsive to said second componenttransmission equalization reference signals separated by said combiningcircuitry.
 54. The receiver of claim 53, further characterized in thatsaid filter weight computation circuitry comprises: a ghost cancellationfilter weight computer responding to said first component transmissionequalization reference signals separated by said combining circuitry todetermine said adjustable filtering weights of said ghost cancellationfilter; and an equalization filter weight computer responding to saidsecond component transmission equalization reference signals separatedby said combining circuitry to determine said adjustable filteringweights of said equalization filter.
 55. The receiver of claim 54,further characterized in that said ghost cancellation filter weightcomputer is arranged to calculate a discrete Fourier transform (DFT) inresponse to said first component transmission equalization referencesignals separated by said combining circuitry and determines saidadjustable filtering weights of the ghost cancellation filter from thatDFT.
 56. The receiver of claim 53, further characterized in that saidcombining circuitry is of a type for separating said first componenttransmission equalization reference signals and said second componenttransmission equalization reference signals by combining an even number,at least four, of said designated lines.
 57. A receiver as set forth inclaim 53, further characterized in that in each of said transmissionequalization reference signals said first component transmissionequalization reference signal precedes said second componenttransmission equalization reference signal.
 58. The receiver of claim57, further characterized in that said filter weight computationcircuitry comprises: a ghost cancellation filter weight computerresponding to said first component transmission equalization referencesignals separated by said combining circuitry to determine saidadjustable filtering weights of said ghost cancellation filter; and anequalization filter weight computer responding to said second componenttransmission equalization reference signals separated by said combiningcircuitry to determine said adjustable filtering weights of saidequalization filter.
 59. The receiver of claim 58, further characterizedin that said ghost cancellation filter weight computer responds to saidfirst component transmission equalization reference signals separated bysaid combining circuitry to calculate a discrete Fourier transform (DFT)therefrom and determines said adjustable filtering weights of the ghostcancellation filter from that DFT.
 60. The receiver of claim 57, furthercharacterized in that said combining circuitry is of a type forseparating said first component transmission equalization referencesignals and said second component transmission equalization referencesignals by combining an even number, at least four, of said designatedlines.
 61. The receiver of claim 53, further characterized in that eachsaid second component transmission equalization reference signalcomprises a pseudo-noise (PN) sequence of a prescribed first length. 62.The receiver of claim 61, further characterized in that said filterweight computation circuitry comprises: a ghost cancellation filterweight computer responding to said first component transmissionequalization reference signals separated by said combining circuitry todetermine said adjustable filtering weights of said ghost cancellationfilter; and an equalization filter weight computer responding to saidsecond component transmission equalization reference signals separatedby said combining circuitry to determine said adjustable filteringweights of said equalization filter.
 63. The receiver of claim 62,further characterized in that said ghost cancellation filter weightcomputer responds to said first component transmission equalizationreference signals separated by said combining circuitry to calculate adiscrete Fourier transform (DFT) therefrom and determines saidadjustable filtering weights of the ghost cancellation filter from thatDFT.
 64. The receiver of claim 61, further characterized in that saidcombining circuitry is of a type for separating said first componenttransmission equalization reference signals and said second componenttransmission equalization reference signals by combining an even number,at least four, of said designated lines.
 65. A receiver comprising:circuitry for recovering a digitized baseband signal by detecting atelevision signal having a succession of frames, each of said framescomprising an odd-numbered field followed by an even-numbered field,each of said fields comprising a specified number of lines with aparticular one of said lines being designated to carry a respectiveghost-cancellation reference signal comprising a first componentghost-cancellation reference signal and a second componentghost-cancellation reference signal of shorter duration than said firstcomponent ghost-cancellation reference signal; separator circuitry forseparating each of said first and second component ghost-cancellationreference signals from said digitized baseband signal; a ghostcancellation filter and an equalization filter connected in cascade forresponding to said digitized baseband signal, each filter havingadjustable filtering weights; and filter weight computation circuitryfor determining said adjustable filtering weights of said ghostcancellation filter responsive to said first componentghost-cancellation reference signal separated by said separatorcircuitry, and for determining said adjustable filtering weights of saidequalization filter responsive to said second componentghost-cancellation reference signal separated by said separatorcircuitry.
 66. The receiver of claim 65, further characterized in thatsaid filter weight computation circuitry comprises: a ghost cancellationfilter weight computer responding to said first componentghost-cancellation reference signals separated by said separatorcircuitry to determine said adjustable filtering weights of said ghostcancellation filter; and an equalization filter weight computerresponding to said second component ghost-cancellation reference signalsseparated by said separator circuitry to determine said adjustablefiltering weights of said equalization filter.
 67. The receiver of claim66, further characterized in that said ghost cancellation filter weightcomputer is arranged to calculate a discrete Fourier transform (DFT) inresponse to said first component ghost-cancellation reference signalseparated by said combing circuitry and determines said adjustablefiltering weights of the ghost cancellation filter from that DFT.
 68. Areceiver comprising: circuitry for recovering a digitized basebandsignal by detecting a television signal having a succession of frames,each of said frames comprising an odd-numbered field followed by aneven-numbered field, each of said fields comprising a specified numberof lines with a particular one of said lines being designated to carry arespective ghost-cancellation reference signal comprising a firstcomponent ghost-cancellation reference signal and a second componentghost-cancellation reference signal of shorter duration than said firstcomponent ghost-cancellation reference signal, said first componentghost-cancellation reference signal being of the same amplitude andsense of polarity in both said odd-numbered field and said even-numberedfield of each said frame, said second component ghost-cancellationreference signal being the same in amplitude in both said odd-numberedfield and said even-numbered field of each said frame but opposite insense of polarity; circuitry for separating from said digitized basebandsignal said lines designated for carrying a ghost-cancellation referencesignal; memory for temporarily storing a number of said designated linesas separated; combining circuitry for separating from saidghost-cancellation reference signals said first componentghost-cancellation reference signal and said second componentghost-cancellation reference signal by combining a most current one ofsaid designated lines with at least one temporarily stored previous oneof said designated lines; a ghost cancellation filter and anequalization filter connected in cascade for responding to saiddigitized baseband signal, each filter having adjustable filteringweights; and filter weight computation circuitry, for determining saidadjustable filtering weights of said ghost cancellation filterresponsive to said first component ghost-cancellation reference signalseparated by said separator circuitry, and for determining saidadjustable filtering weights of said equalization filter responsive tosaid second component ghost-cancellation reference signal separated bysaid separator circuitry.
 69. The receiver of claim 68, furthercharacterized in that said filter weight computation circuitrycomprises: a ghost cancellation filter weight computer responding tosaid first component ghost-cancellation reference signals separated bysaid combining circuitry to determine said adjustable filtering weightsof said ghost cancellation filter; and an equalization filter weightcomputer responding to said second component ghost-cancellationreference signals separated by said combining circuitry to determinesaid adjustable filtering weights of said equalization filter.
 70. Thereceiver of claim 69, further characterized in that said ghostcancellation filter weight computer is arranged to calculate a discreteFourier transform (DFT) in response to said first componentghost-cancellation reference signal separated by said combing circuitryand determines said adjustable filtering weights of the ghostcancellation filter from that DFT.
 71. The receiver of claim 68, furthercharacterized in that said combining circuitry is of a type forseparating said first component ghost-cancellation reference signals andsaid second component ghost-cancellation reference signals by combiningan even number, at least four, of said designated lines.
 72. A receiveras set forth in claim 68, further characterized in that in each of saidghost-cancellation reference signals said first componentghost-cancellation reference signal precedes said second componentghost-cancellation reference signal.
 73. The receiver of claim 72,further characterized in that said filter weight computation circuitrycomprises: a ghost cancellation filter weight computer responding tosaid first component ghost-cancellation reference signals separated bysaid combining circuitry to determine said adjustable filtering weightsof said ghost cancellation filter; and an equalization filter weightcomputer responding to said second component ghost-cancellationreference signals separated by said combining circuitry to determinesaid adjustable filtering weights of said equalization filter.
 74. Thereceiver of claim 73, further characterized in that said ghostcancellation filter weight computer responds to said first componentghost-cancellation reference signals separated by said combiningcircuitry to calculate a discrete Fourier transform (DFT) therefrom anddetermines said adjustable filtering weights of the ghost cancellationfilter from that DFT.
 75. The receiver of claim 72, furthercharacterized in that said combining circuitry is of a type forseparating said first component ghost-cancellation reference signals andsaid second component ghost-cancellation reference signals by combiningan even number, at least four, of said designated lines.
 76. Thereceiver of claim 68, further characterized in that each said secondcomponent ghost-cancellation reference signal comprises a pseudo-noise(PN) sequence of a prescribed first length.
 77. The receiver of claim76, further characterized in that said filter weight computationcircuitry comprises: a ghost cancellation filter weight computerresponding to said first component ghost-cancellation reference signalsseparated by said combining circuitry to determine said adjustablefiltering weights of said ghost cancellation filter; and an equalizationfilter weight computer responding to said second componentghost-cancellation reference signals separated by said combiningcircuitry to determine said adjustable filtering weights of saidequalization filter.
 78. The receiver of claim 77, further characterizedin that said ghost cancellation filter weight computer responds to saidfirst component ghost-cancellation reference signals separated by saidcombining circuitry to calculate a discrete Fourier transform (DFT)therefrom and determines said adjustable filtering weights of the ghostcancellation filter from that DFT.
 79. The receiver of claim 76, furthercharacterized in that said combining circuitry is of a type forseparating said first component ghost-cancellation reference signals andsaid second component ghost-cancellation reference signals by combiningan even number, at least four, of said designated lines.
 80. Atelevision receiver for detecting and processing television signalstransmitted in a succession of frames, each of said frames comprising anodd-numbered field followed by an even-numbered field, each of saidfields comprising a specified number of line s with at least one of saidlines being designated to carry a ghost-cancellation reference signalcomprising a first component ghost-cancellation reference signal and asecond component ghost-cancellation reference signal, said televisionreceiver comprising: an input for collecting said television signals,wherein said television signals include video signals and saidghost-cancellation reference signals; an analog to digital convertercoupled to said input for digitizing said video signals and saidghost-cancellation reference signals collected by said input; a signalcapture processor coupled to said analog to digital converter forreceiving said digitized ghost-cancellation reference signals and forseparating said first component ghost-cancellation reference signal fromsaid second component ghost-cancellation reference signal; aghost-cancellation filter weight computer coupled to said signal captureprocessor for receiving said first component ghost-cancellationreference signal and for responding to said first componentghost-cancellation reference signal to determine a first set ofadjustable filtering weights; and an adjustable ghost-cancellationfilter coupled to said analog to digital converter for receiving saiddigitized video signals and also coupled to said ghost-cancellationfilter weight computer for receiving said first set of adjustablefiltering weights, said adjustable ghost-cancellation filter processingsaid digitized video signals in response to said first set of adjustablefiltering weights.
 81. The television receiver of claim 80 furthercomprising: an equalization filter weight computer coupled to saidsignal capture processor for receiving said second componentghost-cancellation reference signal and for responding to said secondcomponent ghost-cancellation reference signal to determine a second setof adjustable filtering weights; and an adjustable equalization filtercoupled in cascade with said adjustable ghost cancellation filter andalso coupled to said equalization filter weight computer for receivingsaid second set of adjustable filtering weights, said adjustableequalization filter processing signals output by said adjustable ghostcancellation filter in response to said second set of adjustablefiltering weights.
 82. The television receiver of claim 80 furthercharacterized in that said second component ghost-cancellation referencesignal is of shorter duration than said first componentghost-cancellation reference signal.
 83. The television receiver ofclaim 82 further characterized in that said second componentghost-cancellation reference signal is a pseudo-noise (PN) sequence. 84.The television receiver of claim 83 further characterized in that saidfirst component ghost-cancellation reference signal is of the sameamplitude and sense of polarity in both said odd-numbered field and saideven-numbered field of each said frame, and said second componentghost-cancellation reference signal is the same in amplitude in bothsaid odd numbered field and said even-numbered field of each said framebut opposite in sense of polarity.
 85. The television receiver of claim84 further comprising: an equalization filter weight computer coupled tosaid signal capture processor for receiving said second componentghost-cancellation reference signal and for responding to said secondcomponent ghost-cancellation reference signal to determine a second setof adjustable filtering weights; and an adjustable equalization filtercoupled in cascade with said adjustable ghost cancellation filter andalso coupled to said equalization filter weight computer for receivingsaid second set of adjustable filtering weights, said adjustableequalization filter processing signals output by said adjustable ghostcancellation filter in response to said second set of adjustablefiltering weights.
 86. A television receiver for detecting andprocessing television signals transmitted in a succession of frames,each of said frames comprising an odd-numbered field followed by aneven-numbered field, each of said fields comprising a specified numberof line with at least one of said lines being designated to carry aghost-cancellation reference signal comprising a first componentghost-cancellation reference signal and a second componentghost-cancellation reference signal, said television receivercomprising: an analog-to-digital converter for digitizing said analogbaseband signal to generate a digital baseband signal includingdigitized ghost-cancellation reference signals; adaptive digitalfiltering circuitry with adjustable filtering weights, said adaptivedigital filtering circuitry connected for receiving as an input signalthereof said digital baseband signal as supplied from saidanalog-to-digital converter with any accompanying multi-path distortionand for supplying as an output signal therefrom said digital basebandsignal with reduction of any accompanying multi-path distortion; asignal capture processor connected for receiving said digital basebandsignal from said analog-to-digital converter, for retrieving said firstcomponent ghost-cancellation reference signal from said digital basebandsignal, and for retrieving said second component ghost-cancellationreference signal from said digital baseband signal; and filter weightcomputation circuitry, for determining said adjustable filtering weightsof said adaptive digital filtering circuitry responsive to at least oneof said first and said second component ghost-cancellation referencesignals.
 87. The television receiver of claim 86, wherein said adaptivedigital filtering circuitry comprises the cascade connection of: a firstadaptive digital filter; and a second adaptive digital filter, saidfirst adaptive digital filter having a first set of said adjustablefiltering weights; and wherein said filter weight computation circuitryis of a type for determining said first set of said adjustable filteringweights responsive to said first component ghost-cancellation referencesignal.
 88. The television receiver of claim 87, wherein said firstadaptive digital filter is operable as a ghost-cancellation filter. 89.The television receiver of claim 87, wherein said second adaptivedigital filter has a second set of said adjustable filtering weights;and wherein said filter weight computation circuitry is of a type fordetermining said second set of said adjustable filtering weightsresponsive to said second component ghost-cancellation reference signal.90. The television receiver of claim 89, wherein said first adaptivedigital filter is operable as a ghost-cancellation filter and saidsecond adaptive digital filter is operable as an equalization filter.91. The television receiver of claim 90, wherein said first adaptivedigital filter precedes said second adaptive digital filter in theirsaid cascade connection.
 92. The television receiver of claim 90,wherein said second component ghost-cancellation reference signal is ofshorter duration than said first component ghost-cancellation referencesignal.
 93. The television receiver of claim 90, wherein said secondcomponent ghost-cancellation reference signal is a pseudo-noise (PN)sequence.
 94. The television receiver of claim 90, wherein said firstcomponent ghost-cancellation reference signal is of the same amplitudeand sense of polarity in both said odd-numbered field and saideven-numbered field of each said frame, and said second componentghost-cancellation reference signal is the same in amplitude in bothsaid odd-numbered field and said even-numbered field of each said framebut opposite in sense of polarity.
 95. The television receiver of claim86, wherein said adaptive digital filtering comprises the cascadeconnection of: a first adaptive digital filter; and a second adaptivedigital filter, said second adaptive digital filter having a respectiveset of said adjustable filtering weights; and wherein said filter weightcomputation circuitry is of a type for determining said adjustablefiltering weights of said second adaptive digital filter responsive tosaid second component ghost-cancellation reference signal.
 96. Thetelevision receiver of claim 95, wherein said second adaptive digitalfilter is operable as an equalization filter.
 97. The televisionreceiver of claim 96, wherein said first adaptive digital filterprecedes said second adaptive filter in their said cascade connection.98. A receiver comprising: detection circuitry for recovering adigitized baseband signal by detecting a transmitted signal having asuccession of frames, each of said frames comprising an odd-numberedfield followed by an even-numbered field, each of said fields comprisinga specified number of lines with only a particular one of said linesbeing designated to carry a respective transmission equalizationreference signal comprising a first component transmission equalizationreference signal and a second component transmission equalizationreference signal, said first component transmission equalizationreference signals being of the same amplitude and sense of polarity inboth said odd-numbered field and said even-numbered field of each saidframe, said second component transmission equalization reference signalsbeing pseudo-noise (PN) sequences and being the same in amplitude inboth said odd-numbered field and said even-numbered field of each saidframe but opposite in sense of polarity; circuitry for separating fromsaid digitized baseband signal said lines designated for carrying arespective transmission equalization reference signal; retrievingcircuitry for retrieving either of said first component or secondcomponent transmission equalization reference signal from said linesdesignated for carrying said respective transmission equalizationreference signal; an equalization filter with adjustable filteringweights, said equalization filter connected for responding to saiddigitized baseband signal; and an equalization weight computerresponding to either of said first component or said second componenttransmission equalization reference signal retrieved by said retrievingcircuitry to determine said adjustable filtering weights of theequalization filter.
 99. A receiver comprising: circuitry for recoveringa digitized baseband signal by detecting a television signal having asuccession of frames, each of said frames comprising an odd-numberedfield followed by an even-numbered field, each of said fields comprisinga specified number of lines only a particular one of which said lines isdesignated for carrying a respective ghost-cancellation reference signalcomprising a first component ghost-cancellation reference signal and asecond component ghost-cancellation reference signal, said firstcomponent ghost-cancellation reference signals being of the sameamplitude and sense of polarity in both said odd-numbered field and saideven-numbered field of each said frame, said second componentghost-cancellation reference signals being pseudo-noise (PN) sequencesand being the same in amplitude in both said odd-numbered field and saideven-numbered field of each said frame but opposite in sense ofpolarity; circuitry for separating from said digitized baseband signalsaid lines designated for carrying a ghost-cancellation referencesignal; retrieving circuitry for retrieving either of said firstcomponent or said second component ghost-cancellation reference signalfrom said lines designated for carrying said ghost-cancellationreference signal; an equalization filter with adjustable filteringweights, said equalization filter connected for responding to saiddigitized baseband signal; and an equalization weight computerresponding to either of said first component or said second componentghost-cancellation reference signal retrieved by said retrievingcircuitry to determine said adjustable filtering weights of theequalization filter.
 100. A television receiver for detecting andprocessing television signals transmitted in a succession of frames,each of said frames comprising an odd-numbered field followed by aneven-numbered field, each of said fields comprising a specified numberof lines with at least one of said lines being designated to carry aghost-cancellation reference signal comprising a first componentghost-cancellation reference signal and a second componentghost-cancellation reference signal, said television receivercomprising: an input for collecting said television signals, whereinsaid television signals include video signals and saidghost-cancellation reference signals; an analog to digital convertercoupled to said input for digitizing said video signals and saidghost-cancellation reference signals collected by said input; a signalcapture processor coupled to said analog to digital converter forreceiving said digitized ghost-cancellation reference signals and forretrieving said first component ghost-cancellation reference signal fromsaid designated one of said lines; a ghost-cancellation filter weightcomputer coupled to said signal capture processor for receiving saidfirst component ghost-cancellation reference signal and for respondingto said first component ghost-cancellation reference signal to determinea first set of adjustable filtering weights; and an adjustableghost-cancellation filter coupled to said analog to digital converterfor receiving said digitized video signals and also coupled to saidghost-cancellation filter weight computer for receiving said first setof adjustable filtering weights, said adjustable ghost-cancellationfilter processing said digitized video signals in response to said firstset of adjustable filtering weights.
 101. The television receiver ofclaim 100 further characterized in that said second componentghost-cancellation reference signal is of shorter duration than saidfirst component ghost-cancellation reference signal.
 102. The televisionreceiver of claim 101 further characterized in that said secondcomponent ghost-cancellation reference signal is a pseudo-noise (PN)sequence.
 103. The television receiver of claim 102 furthercharacterized in that said first component ghost-cancellation referencesignal is of the same amplitude and sense of polarity in both saidodd-numbered field and said even-numbered field of each said frame, andsaid second component ghost-cancellation reference signal is the same inamplitude in both said odd-numbered field and said even-numbered fieldof each said frame but opposite in sense of polarity.